liblog: test: liblog.__security miscalculation

The gTest should not be able to set ro.device_owner, either as a unit
test or a CTS test.  The CTS test should not be able to set
persist.logd.security, the gTest may as it is run on userdebug with
root, so check if we are root to discern expectations.

Test: gTest liblog-unit-tests --gtest_filter=liblog.__security
Test: cts-tradefed run cts-dev -a armeabi-v7a -m CtsLiblogTestCases -t liblog#__security
Bug: 36480230
Change-Id: I1da88aae34da4e2fca8dd88d740eeb879d9c65bb